The typical bore hole or well drilled to recover gas and oil is created by positioning a drill bit at the lower end of a drill string and rotating the drill string with a force acting through the drill string urging the drill bit against the formation to be drilled. As the drill bit works through the formation, additional drill string sections may be added from the surface until the desired depth is achieved.
During drilling, it is common to provide a drilling mud to cool and clean the drill bit of material cut from the drilling face. The mud flows to the drill bit through the hollow center core of the drill string from a pump on the surface. The mud returns to the surface through the annular space between the drill string and the bore hole.
During the circulation of the mud in the bore hole, gases, such as natural gas or hydrogen sulfide, will be entrained in the mud. Upon reaching the surface, these gases must be eliminated from the mud to prevent combustion. After the mud has been degased and cleansed of debris from the cutting face, it may be reused within the bore hole.
In the typical operation, the mud will flow upward in the bore hole through a blow out preventor, to a bell nipple beneath the rig floor. A flow line then extends from the bell nipple to a shale shaker to remove the cuttings or chips accumulated in the mud. The gas rich mud then flows from the shale shaker into mud tanks for storage. A degaser may be provided on the mud tank which acts to degasify the mud stored therein. A mud gas separator may be employed at the end of the tanks and is used during control drilling or during a blowout or gas kick. When the blow out preventor blocks flow through the low pressure bell nipple it directs the mud flow through a high pressure vent line to the mud gas separator. A gas kick occurs when a sufficiently large volume of gas is entrained in the mud flow to interrupt the flow of the mud. A blowout will occur if sufficient gas is entrained to reduce the hydrostatic head of mud in the bore hole to where it will not maintain the hydrocarbon reserves within the hole. Finally, a vacuum blower system may be employed on the rig to draw out the gas impregnated air about the bell nipple and under the rig floor for the safety of the men working on the rig.
One system of mud degasification is described and illustrated in U.S. Pat. No. 2,748,884 issued June 5, 1956. In this apparatus, gas filled mud may travel from the choke manifold or shale shaker into a mud trough. The mud tank may then pass into a shale shaker and mud tanks or pits. A mud degaser tank is positioned above the mud trough and picks up the gas filled mud by vacuum through a suction pipe. The mud passes downwardly over a series of cascade plates within a vacuum to remove the entrained gases.
However, a need has arisen to simplify and improve the procedure of mud degasification and treatment. A need also exists to combine the functions of degaser, mud gas separator and vacuum blower system in a single inexpensive reliable device. A critical concern is the mobility of a device for treating and degasing drilling mud so that the device may be transferred from site to site without great effort.